The invention disclosed herein is a lumber edger.
After logs are sawed into common board thicknesses such as one, two, four or six inches, the boards are passed through edgers which cut off the generally round edges and produces a board which has square edges and a width falling usually within one of several standard width classifications. After edging, the boards pass through a trimmer which trims their ends to achieve a final board length. Edgers which are in such widespread use as to be considered the standard of the lumbering industry were introduced several decades ago and are still basically the same as they were at the time they were introduced. It seems to have become an accepted fact that conventional edgers necessarily had to occupy the great amount of space that they do and that the lumber had to be handled in one specific fashion in order to produce the necessary results. In prior art edger machines two saw blades are motor driven and arranged in adjustable spaced relationship relative to each other so that a board of predetermined width including its edge irregularities can be pushed between the blades for trimming opposite edges at the same time. There are usually pairs of pressure generating rollers on the in-feed and out-feed side of the saw blades through whose nip the board is passed as it is being edged. Since the board is in motion relative to the saw blades, the board can never be gripped positively. A consequence of this is that when the saw blades bind in a board periodically, the high velocity saws may eject the board at high velocity and damage surrounding machinery and seriously injure or kill the machine operator despite safety precautions that are taken. It is known that boards can be ejected from conventional edgers at initial velocities of as high as 10,000 feet per minute which confirms the hazard of working around prior art edgers. Of course, some purported safety guards have been devised such as hanging heavy chains adjacent the line of movement of the boards, at least on the side where the operator stands. Sometimes, however, the pieces that are being trimmed from the board are ejected like arrows and, because they are relatively small in cross-section, it is very difficult to provide safety barriers to stop them.
Another generally recognized disadvantage of conventional edgers is the amount of space they occupy in the lumber mill. In conventional edgers, the boards are conducted to the edger on an in-feed conveyor which is wide enough to accommodate the longest board obtainable from the longest log length sawed in the particular mill. In other words, the length of the boards lie across the width of the conveyor. At the end of this in-feed conveyor, the boards are transferred to another conveyor moving perpendicular to the in-feed conveyor which directs the boards toward the saw blades. After being transferred from the in-feed conveyor to the conveyor that conveys the boards to the saws, the boards have changed direction and their lengths are aligned with the length of the conveyor. After passing through the saws and undergoing edging, the boards are passed on to an output conveyor which can be no shorter than the longest board expected to be treated nor can it be any shorter than the conveyor on the input side of the saws. The boards make another change in direction as they leave the output conveyor and go on to a final conveyor that is running perpendicular to the output conveyor. The final conveyor usually directs the boards to an end trimmer. Thus, in the prior art edger installations, there are four separate conveyors which change the direction of the boards twice. Disadvantages of this arrangement are that a large amount of energy is required to drive the plurality of the conveyors, capital costs are high, more maintenance is required for the conveyors, and the apparatus takes up a large amount of space.